Rather than the mess (see wavy pattern on TOS background) that you have now.
I use mine with Amiga (OCS, ECS, AGA), VGA and a Wii.
OSSC Pro is costly, in good part due to cost of FPGA and other components used, but the simpler OSSC is typically under $100.
OSSC Pro is able to buffer full frames, deinterlace and have different input and output timings, whereas OSSC operates with only a couple of lines of video data, thus is less flexible, but sufficient for most uses, with excellent low latency.
If you need wildly different timings for the output, you'll want the Pro, which unfortunately isn't cheap.
As for "will it capture this weird mode?" general question, it will. It does have tremendous sampling flexibility. IMHO the main selling point of the OSSC.
I haven't tried the OSSC Pro, but the Retrotink 4k should probably also work fine and is really easy to use. A bit on the expensive side though...
Definitely easier to use, but nowhere as flexible.